Fix to event listener issue as per https://bugzilla.mozilla.org/show_bug.cgi?id=1451699#c1

src/privileged/introductionNotificationBar/schema.json

@@ -15,16 +15,19 @@
     "events": [
       {
         "name": "onIntroductionShown",
+        "type": "function",
         "description": "Description of the event",
         "parameters": []
       },
       {
         "name": "onIntroductionAccept",
+        "type": "function",
         "description": "Description of the event",
         "parameters": []
       },
       {
         "name": "onIntroductionLeaveStudy",
+        "type": "function",
         "description": "Description of the event",
         "parameters": []
       }